Tannins (amber water)

Organic compounds released by wood and leaves that colour the water yellow-brown. They create the blackwater effect loved by many tropical fish.

Detailed explanation

Tannins are polyphenols released by the decomposition of wood and leaves. In nature they colour the black waters of the Amazon.

The effects of tannins include: slight lowering of pH, antibacterial and antifungal properties, reduction of stress in fish.

The fish that benefit from it are: Betta, Discus, Apistogramma, cardinals, rasbore, Caridina shrimp.

The blackwater aquarium intentionally replicates these conditions with driftwood, Catappa leaves and peat extracts.

Activated carbon removes staining. Boiling woods before use reduces initial release.

Catappa (Indian almond) leaves are particularly popular. Shrimps love them and feed on them.